Low levels of lead, previously considered safe, have been found to cause high blood pressure and strokes in adults and to adversely affect the development, mental abilities and hearing of children. Most of the lead in water that is consumed originates from corrosion in water-delivery systems and home plumbing. Drinking water delivered from municipal and other water suppliers is not normally high in lead content. Thus, the primary source of lead is derived from subsequent corrosion of service connections, pipes, fixtures and other plumbing parts of systems which distribute water to end consumers. Much of this lead-bearing plumbing is privately owned, that is, it is installed permanently within homes and buildings. Because of this, as a practical matter, the reduction of lead in drinking water has been accomplished primarily by introducing into the drinking water corrosion inhibitors, by adjusting the alkalinity level of the water by raising its pH value to eight, by service connection replacements of water distribution systems to homes or buildings, and by public education concerning the danger of lead in drinking water. Substantial levels of lead have also been found in water delivered to drinking fountains such as those installed in office buildings, schools and other public facilities.
The replacement of plumbing in a home or other building is seldom a practical solution to achieve the desired reduction of lead and other heavy metals in drinking water at point-of-use.
Purification of water at point-of-use is a more logical solution to the problem. Conventional technologies which can be used for this purpose include reverse osmosis, distillation, and filtration utilizing activated carbon and ion-exchange resins. Reverse osmosis and activated carbon filtration units have been widely employed for home drinking water treatment to remove a variety of contaminants, primarily organics from drinking water. These filtration units can also remove lead. Further, distillation and ion-exchange resin units are also effective in removing lead from drinking water. These technologies, however, are non-specific in that they are not directed primarily to the removal of lead and other heavy metals, and for this reason their lead-removal capacities for drinking water are significantly less than might otherwise be the case. The situation is aggravated if alkalinity of the water is increased or corrosion inhibitors are added, which are frequent methods utilized by water treatment plants to reduce the corrosivity of their treated water. Current systems of reverse osmosis do not work well using line pressures which exist in most homes. In addition, their capacities to produce purified water are relatively low. A high pressure pump needs to be added which may prove expensive and impractical. Single-stage distillation units are quite energy intensive and, for this reason, generally should be avoided. Thus, most known technologies for reducing lead and other heavy metals in drinking water at point-of-use are either capital intensive or costly to operate, or both.
The use of alumina for water filters is known. In addition, gamma alumina is known to be selective for heavy metals. Unfortunately, the prior art experience with alumina has not demonstrated that this filtration substance to be a satisfactory solution for point-of-use filtration of drinking water at most locations from the standpoints of efficiency and capacity.
The following is a list of literature and other publications which reflect the skill of the art and, for such purposes, are incorporated herein by reference:
1. Lippens, B. C. and Steggerda, J. J. (1970) Active Alumina. In Physical and Chemical Aspects of Adsorbents and Catalysts (B. G. Linsen, Ed.). Academic Press, New York, N.Y. PA1 2. Srivastave, S. K. et al. (1988) Studies on the Removal of Some Toxic Metal Ions from Aqueous Solutions and Industrial Waste. Part I (Removal of Lead and Cadmium by Hydrous Iron and Aluminum Oxide). Environ. Tech. Letters 9, 1173-1185. PA1 3. Hohl, H. and Stumm, W. (1976) Interaction of PB.sup.2+ with Hydrous.alpha.-Al.sub.2 O.sub.3. J. Colloid Interface Sci. 55, 281-288. PA1 4. Huang, C. P. et al. (1986) Chemical Interactions Between Heavy Metal Ions and Hydrous Solids. In Metal Spectation, Separation, and Recovery (J. W. Patterson and R. Passino, Eds.). Lewis Scientific Publishing, Comp., New York, N.Y. PA1 5. Bilinski, H. et al. (1975) Copper and Lead in Natural Water. Vom Wasser 43, 107-116. PA1 6. Murray, J. and Brewer, P. G. (1977) Mechanisms of Removal of Manganese, Iron and Other Trace Metals from Sea Water. In Marine Manganese Deposits (G. P. Glasby, Ed.) Elsevier Scientific Publishing Company, New York, N.Y. PA1 7. Grahame, D. G. (1955) Electrical Double Layer. J. Chem. Physic. 23, 1166-1176. PA1 8. Levine, S. and Smith, A. L. (1971) Theory of Differential Capacity of the Oxide-Aqueous Electrolyte Interface. Dis. Fara. Soc. 52, 290-301. PA1 9. Matijevic, E. et al. (1960) Detection of Metal Ion Hydrolysis by Coagulation: II. Thorium. J. Phy. Chem. 64, 1157-1161. PA1 10. Matijevic, E. et al. (1966) Stabilization of Lyophobic Colloids by hydrolyzed Metal Ions. Faraday Soc. 42, 187-196. PA1 11. James, R. O. and Healy, T. W. (1972) Adsorption of Hydrolyzable Metal Ions at the Oxide-Water Interface. Parts I, II and III. J. Colloid & Interface Sci. 40, 42-81. PA1 12. Stanton, J. and Maatman, R. W. (1963) The Reaction Between Aqueous Uranyl Ion and the Surface of Silica Gel. J. Colloid Sci. 18, 132-146. PA1 13. Dugger, D. L. et al. (1964) The Exchange of Twenty Metal Ions with the Weakly Acidic Silanol Group of Silica Gel. J. Phys. Chem. 68, 757-760. PA1 14. Huang, C. P. and Stumm, W. (1973) Specific Adsorption of Cations on Hydrous.alpha.-Al.sub.2 O.sub.3. J. Colloid & Interface Sci. 43, 409-420. PA1 15. Stumm, W. et al. (1970) Specific Chemical Interaction Affecting the Stability of Dispersed Systems. Croatica Chem. Act 42, 223-228. PA1 16. Baes, C. F. and Mesmer, R. E. (1976) The Hydrolysis of Cations. John Wiley & Sons, Inc., New York, N.Y. PA1 17. Farley, K. J. et al. (1985) A Surface Precipitation Model for the Sorption of Cations on Metal Oxides. J. Colloid & Interface Sci. 106, 226-242. PA1 18. Elliott, H. A. and Huang, C. P. (1984) Factors Affecting the Adsorption of Complexed Heavy Metals on Hydrous-Al.sub.2 O.sub.3. Wat. Sci. Tech. 17, 1017-1028. PA1 19. Kummert, R. and Stumm, W. (1980) The Surface Complexation of Organic Acids on Hydrous.alpha.-Al.sub.2 O.sub.3. J. Colloid & Interface Sci. 75, 373-385. PA1 20. Kim, J. S. (1988) Characteristics of Humic Substances and Their Removal Behavior in Water Treatment. Ph.D. Dissertation, Georgia Institute of Technology, Atlanta, Ga. PA1 21. Chian, E. S. K. et al. (1987) Comparison of High Molecular Weigh Organic Compounds Isolated from Drinking Water in Five Cities. In Organic Pollutants in Water, Advances in Chemistry Series 214, American Chemical Society, Washington, D.C. PA1 22. APHA-AWWA-WPCF (1985) Standard Methods for the Examination of Water and Wastewater, 16th edition. American Public Health Association, Washington, D.C. PA1 23. The Environmental Chemistry of Aluminum, (1989) CRC Press, Inc. Boca Raton, Fla. PA1 24. Principles of Electroplating and Electroforming, W. Blum and G. Hogaboom, 1st Ed., Chapter XVII, McGraw-Hill Book Company, Inc., New York, N.Y.